1. Field of the Invention
The present invention relates generally to apparatuses and methods for the inspection of access structures, vertical shafts, tunnels, and other conduits, and more specifically, to apparatuses and methods for the inspection of manholes to catalog their locations and general conditions including size, shape, appearance, structural condition (e.g., manhole ring, walls, and inverts), and location of lateral connections.
2. Description of the Background
Manholes provide access to sewer systems at the surface and extend down to sewer pipes. Manholes and other access structures are essential to the ongoing inspection, maintenance, and renovation of sewer systems. Inspection of manholes provides valuable information for maintenance and repair of sewer systems. Prior art methods of manhole inspection, however, do not provide comprehensive, repeatable, and measurable inspections.
Although practices for manhole inspection have not been standardized, practices and procedures for pipeline inspection have been well established. Oversight organizations in the United States such as the National Association of Sewer Service Companies (NASSCO) have developed defect codes to provide standards for the way in which defects in pipes are classified and rated. These standards are used to develop inventories of assets and conduct condition assessments of those assets using a standard approach. Standardization not only provides a better opportunity for data quality control, but also extends the shelf life of the data, leverages the use of data for many more purposes and creates an environment to actually monitor the rate of deterioration over time.
Inspection methods for pipes gather data in a manner to take advantage of those standards. These methods include the use of a remotely controlled, tethered mobility tractor or sled, a color, pan, tilt, zoom camera, and sometimes a light-based sensor to accurately measure pipe internal characteristics. A payout sensor mounted near a cable storage reel provides distance down a pipe in order to tag defects to a known location in the pipe. These methods are accepted in the industry to provide inspection data that can be analyzed to NASSCO standards.
While NASSCO has released a set of defect codes and rating standards that relate to manhole inspection, no current method provides thorough, consistent, and repeatable inspection of manholes. Current methods thus do not take advantage of those standards.
Traditional manhole inspections have been more of a survey, with inspectors looking for signs of water infiltration during wet weather events. The purpose of those surveys is to identify which manhole covers could be repaired or replaced to reduce infiltration problems.
Manhole inspections are performed to inventory collection system assets, to update collection system maps and to determine the structural condition of each manhole. Much of manhole inspection performed to date has been conducted by specialty firms that have individualized processes for collecting and interpreting manhole condition data. Those data are typically intended for specific project use and not for long term asset management. Differences in terminology, inspection forms, amount of detail, training, and database formatting generate condition assessment data that are inconsistent and difficult to use and compare. As with pipe inspection, manhole inspection can greatly benefit from a consistent approach to data collection and analysis.
Methods used to collect inspection data also vary widely. The least sophisticated and most dangerous of these methods is human entry into the manhole. This is less than desirable, as the inspector's safety is jeopardized by the confined space entry. Further, observations that are made are subjective in nature. In addition, no image data is typically recorded.
Some prior art approaches employ photography and camcorders along with flashlights and spotlights to collect visual inspection data from the ground level. This approach is safer for the inspector, but limits the ability to thoroughly inspect and identify all defects, some of which may be at the bottom of the manhole and difficult to assess from ground level. It is also very difficult to collect comprehensive image data so that the entire manhole is recorded in detail. In this scenario, the inspector still subjectively identifies and photographs defective areas of the manhole.
Another current practice for manhole inspection involves the use of a pan, tilt, zoom camera with lights mounted to the end of a telescoping pole. This device is lowered into manholes from ground level and provides better imagery. This method improves on previous approaches by collecting images at various elevations, theoretically allowing a more thorough inspection. However, this approach is still inadequate, as distance to the defect from ground level is not accurately determined. Distance is estimated or a tape measure is placed in the manhole and shown in the image to provide a reference.
All of the above methods fall short of providing a comprehensive, repeatable, and measurable inspection method. First, data from the entire manhole cannot be readily captured by photographs and/or video in sufficient detail. Comprehensive image assessment of the manhole interior allows for proper inspection verification and validation and time-based analysis. Second, traditional methods of manhole inspection fail to generate accurate, measurable data. Such information is valuable when deciding on suitable rehabilitation methods such as liners, inserts, or spray coatings. Further, the data that are captured are not easily stored or integrated into existing sewer asset management software or Geographic Information System (GIS) database systems.
Furthermore, each inspection typically results in a manhole inspection form being filled out by hand and provided to the customer. The customer form is completed by the contractor providing the inspection, with hand-drawn graphical representations of lateral connections, missing bricks, structural damage, and the like. Images are appended to the report as evidence of the defects located during inspection. Engineers can only interpret the results that the inspector has recorded. The engineers cannot validate or verify the inspection unless the inspection were repeated and witnessed at the time of inspection.
Thus, there has been a long-standing need for accurate, comprehensive, and repeatable inspection of manholes and other substantially vertical voids. By providing comprehensive imaging and integrated data collection, the present invention provides thorough manhole inspection data that can be standardized and used to monitor conditions over time. Further, the present systems, apparatuses, and inspection methods could be expanded to a wide variety of voids or conduits in addition to manholes.